Process of developing photographic plates and films.



UNITED STATES PATENT onnron;

- HARRY M. PRINDLE, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO ALFRED H. HILDRETH, TRUSTEE, 0F CAMBRIDGE, MASSACHUSETTS.

PROCESS OF DEVELOPING PHOTOGRAPHIC PLATES AND FILMS.

Specification of Letters Patent.

Patented June 11, 1912.

No Drawing. Application filed May 18, 1904, Serial No. 208,616. Renewed September 30, 1911. Serial No. 652,180.

To all whom it may concern: 1

Be it known that I, HARRY M. PRINDLE, a citizen of the United States, residing in Boston, in the county of Suffolk and State of Massachusetts, have invented a new and useful Improvement in Processes of Developing Photographic Plates and Films, of which the following is a specification.

This invention has' for its principal object to enable the plate-holder to be loaded in subdued daylight, twilight, or by artificial light, such as gas or electricity, and the plate removed from the plate-holder or a film removed from the camera in the same or similar. light, and said plate or film developed in the same or similar light, without any necessity for a dark room or ruby light.

In this,process:First, the plate or film after having been removed from the plateholder or camera is, in subdued actinic light, such as daylight, or artificial light, immersed in a bath (which may be in an open tray) consisting of water and bichlorid of mercury. Preferably sodium chlorid is also used as it increases the solubility of the bichlorid of mercury. The following proportions have been found to give satisfactory results: water 16 parts, blchlorid of mercury 1 part, sodium chlorid 1 part. Second,

Y the plate or film is (still in subdued daylight, or artificial light) immersed in any suitable developer, such as metol and carbonate of potassium to which 2 to 5 drops of bromid of potassium have been added, or hydrochinon developer, said developing solution being in an open tray, and no dark room or ruby light being necessary. Third,

the plate or film is removed from the developing compound and washed in water or other suitable liquid. Fourth, the plate or film is placed in a fixing bath of, say, sodium thiosulfate and water.

The third and fourth steps of the process are old in themselves considered, and the second step is old in itself considered except thatittaken in artificial light or subdued daylight.

By means of this process, a plate which has been inserted in the plate-holder in artifici 1 light or subdued daylight, or a plate a. mm which has been removed from the holder or camera by a similar light, may be developed without employment of a dark room or ruby light, but by bright artificial light, or subdued sunlight or twilight. It is found in practice that by this process the image is held perfectly, and halation is practically done away with.

When this developing process is to be employed, it is permissible and perhaps advisable, that the exposure should be a little longer than is usually the case, and an overexposure, unless it is very excessive, is not injurious; and by means of. this somewhat longer exposure, and the latitude which may be allowed in the exposure, the objects in shadows, or sub-shadows, are broughtout with a greater degree of detail.

Of course the different steps in the above process may be taken in darkness, or by ruby light, if desired, but no better effect is produced;

This process is especially useful where plates or films have become light-struck or fogged either before or after they have been exposed in the camera, many of such plates and films which would otherwise be absolutely worthless giving good results when developed according to this process.

Having thus fully described my invention,

graphic plates or films, consisting in immersing the plate or film, while in subdued actinic light, in a bath comprising water, bichlorid of mercury and sodium chlorid;

then immersing the plate or film in a suit-- able developer; then washing the plate or film; and finally placing the plate or film in a fixing bath, substantially as herein described.

The process of developing photographic plate", or films, consisting in immersing the plate or, film, while in subdued actinic light, in an open or exposed bath comprising water, bichlorid of mercury and sodium chlorid; then immersing the plate or film in a suitable developer contained in an open tray; then Washing the Plate 01' film, and Intestimony whereofl have signed my finally placing the plate 01' film in :1 fixing name to this specification in the presence'of 10 bath, substantially as herein described.

4. The PYUCGSQOf Original development of photographic plates or films which consists in first subjecting the plate 01' film t0 the action of hichlorirl of mercury, and'thereafter developing and fixing the same.

two subscribing Witnesses.

HARRY M. PBINDLE. \Vitnesses: i

' HENRY W. WILLIAMS,

A. K. H001); 

